Here is something I noticed recently....
I was testing something with one of my engines, an older MTH F3 with PS2. I noted that at high speeds, it has a tendency to spark from the rollers pretty substantially and arc slightly from the wheels. Thought that was odd....
I then turned the cruise off and it REALLY sparked!
Then I was curious - I tried other engines, various PS3 and PS2 engines I have. Some would spark just like the F3 and others wouldn't spark at all at high speeds.
I used to have several Williams engines that would do the same thing - at home and at the club layout.
I've cleaned the heck out of the wheels and track and rollers and still see the sparking. Could it be that the speeds cause the rollers to bounce and make less than perfect contact?
I use tubular track and MTH Z-1000s in Conventional only.
EDIT: I've found engines with 4 pick up rollers won't spark at all. All others will at high speeds. No issue at low speeds. I've always had this issue with my engines both at home and on the club layout. Also in DCS at high speeds. Could the rollers be bouncing causing this issue?